Session: VIB-02/MSNDC-10-03

Paper Number: 148028

148028 - Nonlinear Modal Interaction Identification in Kth-Nasa Generic Fighter in Supersonic Flow in Transonic Dynamics Tunnel 

The purpose of this paper is to report findings from the analysis of the KTH-NASA generic fighter aeroelastic wind tunnel data revealing global modal interactions in this system caused by multiple resonance capture events and initiated by local nonlinearities. The generic fighter is a dynamically-scaled wind tunnel model used as a testbed for gathering transonic aeroelastic data. It is shown that during supersonic testing at the Transonic Dynamics Tunnel, vibro-impacts at the embedded external fuel tank shakers on the inboard underwing stations of the generic fighter introduce strong nonlinearity that give rise to nonlinear modal interactions. Specifically, time-frequency analysis of the acceleration data demonstrates that 6:5 and 7:6 transient resonance captures occur across the aircraft exclusively during this vibro-impact forcing window. Further analysis suggests that these resonance captures are dependent on Mach number. These results show experimentally that local vibro‑impacts can cause global nonlinear effects in an aeroelastic system. The data-driven analysis scheme employed shows applicability to full-aircraft flight test data for identifying nonlinear modal interactions. Ultimately, this study substantiates further the observation that local vibro-impacts can cause global nonlinear responses across an aircraft. This needs to be taken into account in aeroelastic and structural designs. The data‑driven analysis flow used herein is effective in identifying nonlinear modal interactions in a broad range of systems and processes, and can find use in identification of LCO and other nonlinear phenomena in flight test data of full-scale aircraft and in other aerospace applications.

Presenting Author: Benjamin Chang University of Illinois at Urbana-Champaign

Presenting Author Biography: Benjamin Chang is a PhD student at the University of Illinois at Urbana-Champaign and a Flutter and Dynamics Engineer at the Naval Air Warfare Center Aircraft Division. He has experience in aeroelastic airworthiness certification, modal testing, and flight test data analysis for the U.S. Navy. His academic research is centered around nonlinear (computational) dynamics/aeroelasticity and modal testing.

Authors:

Benjamin Chang University of Illinois at Urbana-Champaign
Lawrence Bergman University of Illinois at Urbana-Champaign
Keegan Moore University of Nebraska - Lincoln
Walter Silva NASA Langley Research Center
Alexander Vakakis University of Illinois at Urbana-Champaign